1. Field of the Invention
The present invention relates to a vehicular image processing device for processing an image of the circumference of a vehicle acquired by a photographing unit, and a vehicular image processing program causing a computer to perform the mentioned process.
2. Description of the Related Art
Conventionally, there has been known an art configured to process an image of the circumference of a vehicle acquired by a photographing unit and recognize a lane mark such as a white line or the like on a road where the vehicle is travelling, or a subject such as a pedestrian, another vehicle or the like present in the circumference of the vehicle (for example, refer to Japanese Patent Laid-open No. H7-200997). According to the art, information can be provided to a driver or the travel of the vehicle can be controlled according to the recognition result of the lane mark or the subject.
In each processing cycle, the vehicular circumference recognizing device of the conventional art receives an image of the front side of the vehicle photographed by a camera mounted in the vehicle, sets a window for the processing subject in the image, sets the color of a lower portion of the window as the reference color for a road surface area (an area except the white line inside the road), sets an area with color similar to (color similarity is greater than a predefined value) the reference color as the road surface area, and differentiates the road surface area from the non-road surface area (the white line or the non-road area). Thereafter, the device performs detection of the white line, namely detects a straight line obtained respectively from the left and right boundaries of the differentiated road surface area as an edge portion of the white line. Herein, the window is set to a single one in the image according to the positions of the two white lines detected in the previous processing cycle, or according to a fixed value set on the basis of a predefined road information such as the width of a road or the width of a travel lane.
However, after a road is repaired, sometimes a repaired position or a local shadow may be left on the road surface. Most possibly, the repaired position has color locally different from the ambient road surface. Further, the local shadow portion, due to the color further added according to the scattering light only, may have color deviated from the ambient road surface.
Therefore, according to the vehicular circumference recognizing device of the mentioned conventional art, the local repaired position or the local shadow portion in the window may be differentiated as the non-road surface area due to the deviation of color from the reference color. Since the white line is detected according to the boundary therebetween, the white line may be detected with error. In the case of using luminance instead of color, the same result will be obtained.
Moreover, the color of a road surface may vary in the road surface area, for example, when time passes or the color thereof is not identically defined by government. Thus, it is supposed that a wide partial area with color different from the ambient area is present in the road surface area. When the partial area is present, it is difficult for the device in the conventional art mentioned above to use the color of the lower portion in the window as the reference color of the road surface to differentiate the road surface area from the non-road surface area.
In other words, when the color in the road surface area is not identical, it is difficult to set the reference color and the conditions for defining a color similar to the reference color appropriately. If the setting is loose, the lane mark will be included in the road surface area; on the other hand, if the setting is strict, the portion area will be differentiated as the non-road surface area. Thereby, the boundary between the road surface area and the non-road surface area will be obtained with error. Since the white line or a proceeding vehicle is detected according to the boundary obtained with error, the white line or the proceeding vehicle may be detected with error. In the case of using luminance instead of color, the same result will be obtained.